This invention is directed to improved circuitry for driving a horizontal output transformer of the type used in television receivers.
Television receivers, video monitors, and other types of display devices generally develop high voltage for a cathode ray tube by means of a horizontal output transformer. Current is switched off and on in the primary of the output transformer to develop a high voltage pulse in the transformer's secondary. That high voltage pulse is typically rectified and applied as an accelerating potential to a cathode ray tube.
To develop the switched current in the transformer's primary winding, that winding is coupled in series with a horizontal output transistor which is switched off and on at a rate equal to the horizontal scan frequency. The horizontal output transistor is, in turn, conventionally driven by horizontal rate pulses supplied by a driver transformer.
A driver transformer has been commonly used to insure that the horizontal output transistor is turned off and on properly. Although this transformer operates satisfactorily, a serious drawback resides in its relatively high cost as compared to other types of circuit components. Replacing the driver transformer with less expensive, but equally reliable circuitry, is a goal which is obviously desirable but which has not been achieved.
Accordingly, it is a general object of the invention to provide improved driving circuitry for a horizontal output transformer.
It is a more specific object of the invention to provide a transformerless driving circuit for a horizontal output transformer.